Muskrat

Name and taxonomy

Carl Linnaeus described the muskrat in 1766. The genus name Ondatra is a Huron word, ondathra, that reached Latin by way of French. The species name zibethicus means musky and refers to the scent the animal uses to mark its ground. The English name probably comes from an Algonquian word, either muscascus, meaning it is red, or the Abenaki moskwas. The old English name musquash keeps that root, and musk-beaver was another early form.

The muskrat is the only living species in its genus. It belongs to the family Cricetidae, which holds the voles, lemmings, hamsters and most American mice. Sixteen subspecies are recognised across North America. German speakers call it the Bisamratte, and French speakers the rat musque.

Evolution and relatives

The muskrat sits in the subfamily Arvicolinae, the voles and lemmings. It is by far the largest member of that group, likely several times the weight of any vole. Its closest living relative is the round-tailed muskrat, Neofiber alleni, of Florida. That smaller species fills the same role in Florida, where the common muskrat is absent. Alligator predation may be part of the reason the common muskrat never settled Florida.

Like its vole relatives, the muskrat has rooted molars and front teeth that never stop growing. Fossil molars record a slow change in shape over time, which palaeontologists use to date deposits. Muskrat numbers rise and crash over a six to ten year cycle, much as lemming numbers do.

Appearance

A muskrat is 40 to 70 centimetres long in total, and the tail makes up about half of that. It weighs 680 to 1,800 g, about four times a brown rat, though it is only a little longer. The body is thick and rounded, the head is large, and the ears almost vanish in the fur. Short, dense fur is medium to dark brown or black above and paler below, and it greys with age. The coat has two layers that trap air, which keeps the animal warm and buoyant in cold water.

The tail is scaly, almost hairless, and flattened from side to side. It drags on the ground when the animal walks, which leaves an easy track to recognise. The large hind feet are partly webbed, and stiff hairs along the toes widen them for swimming. The front feet are small and serve for digging and for holding food. The lips close behind the front teeth, so the muskrat can gnaw under water without swallowing it.

Habitat and range

Muskrats live in marshes, swamps, ponds, lakes, slow rivers and streams. They favour water deep enough to stay open in winter, and marshes where the level stays steady. In banks they dig burrows with an entrance 15 to 20 centimetres wide below the water line. In open marsh they pile cut plants and mud into domed lodges up to 90 cm tall. Smaller feeding platforms and feeding houses stand nearby.

The native range runs from the tree line in Canada south to the Gulf of Mexico and the lower Colorado River. Five animals, two males and three females, were freed in a park at Dobris in Bohemia in 1905. Their descendants now occupy central and northern Europe, Ukraine, Russia, Siberia, parts of China and Mongolia, north-east Korea and Honshu. Other releases put muskrats in southern Chile and Argentina. GBIF holds records from 53 countries, which includes both native and introduced ground.

Muskrats also use canals and irrigation ditches that people dig. They can live on streams polluted by mine drainage where fish and frogs die. New Zealand bans their import as a prohibited new organism.

Diet and feeding

Plants make up about 95% of the diet. Cattails come first, and muskrats dig for the roots and the thick bases of the stems. They also eat yellow water lily and many other water plants. A muskrat eats about a third of its own weight each day. Near farms it takes maize and other crops that grow close to water.

The rest of the diet is animal food: freshwater mussels, crayfish, frogs, fish and small turtles. In winter it swims under the ice along fixed trails to reach plants on the bottom. It stores no food, but it sometimes eats the inside walls of its own lodge. Muskrats and beavers often share a pond, and a BBC film showed a muskrat feeding from a beaver's store.

Behaviour and social life

A muskrat family is a male, a female and their young of the year. Each family holds a territory, and most activity stays within 15 metres of the lodge or burrow. Females defend the ground more fiercely than males. In spring, muskrats fight over territory and mates, and many are hurt or killed. Up to 40% of a population moves in March and April to find empty ground, and males move about 3 kilometres.

Muskrats are active at any hour, but most of all from mid afternoon until just after dusk. They stay in the water for most of the day, and they swim under it for 12 to 17 minutes. The webbed hind feet push, and the flat tail steers. On land they move slowly. In snow they plug the lodge openings with plants and replace the plug every day.

When a marsh is overcrowded, a female drives her own young out of the group. Crowded groups also fight more, and cannibalism occurs. Young leave their mother's range after their first winter.

Communication and senses

Musk is the main signal. Glands near the base of the tail produce it in both sexes. The scent marks territory, warns off intruders and carries breeding cues. Muskrats also squeak and squeal.

Sight, hearing and smell are all poorly developed. The animal can close its ears against water when it dives. Its body tolerates a build-up of carbon dioxide better than most mammals, as seals and whales do. Its whiskers probably guide it under ice and in murky water.

Reproduction and life cycle

In the southern United States muskrats breed all year. In the north they breed from March to August, and the first litters arrive in late April or May. Gestation lasts 29 to 30 days. A litter holds six to eight kits, and a female bears two or three litters a year. Northern females have larger litters than southern ones.

Kits are born blind and almost hairless, and each weighs about 22 grams. They can swim at about 10 days and eat green plants by 21 days. They are weaned at 3 to 4 weeks and independent at about 30 days. By two months the tail has flattened into its adult shape. A muskrat reaches adult size in about 200 days.

Southern muskrats mature in six months, northern ones in about a year. A wild muskrat lives about 3 years, and captive animals are said to reach 10. AnAge notes that the captive figure is unconfirmed.

Predators and threats

Muskrats feed a long list of predators. Mink, foxes, coyotes, wolves, black bears, lynx and raccoons take them on land and at the lodge. Great horned owls, gyrfalcons, goshawks, bald eagles and golden eagles take them from above. Pike, snapping turtles, alligators and cottonmouths take them in the water. A muskrat escapes by diving, and it can stay down for up to 15 minutes.

In the former Soviet Union the golden jackal is the worst enemy. In the winter of 1948 to 1949 on the Amu Darya, jackals destroyed 71% of muskrat houses, and 16% of those froze. Caribou, moose and elk eat the plant walls of lodges in hard winters. The animal is sensitive to sudden temperature swings, and hot dry weather harms it. Loss of wetlands is the long-term threat, along with trapping and disease.

Population and conservation

The IUCN lists the muskrat as Least Concern. It is widespread and abundant, and fast breeding lets populations absorb trapping, disease and predators. One subspecies, Ondatra zibethicus ripensis, is listed as Data Deficient. Numbers cycle up and down over six to ten years.

A 2024 report in Hakai Magazine found declines of at least half in 34 US states. In a few states the fall was 90 to 99%. Rhode Island holds about 15% of the muskrats it had a few decades ago. The decline began in the 1990s and early 2000s, and its cause is not settled.

In Europe the picture is reversed. The European Union added it to its register of invasive alien species on 2 August 2017. Belgium, France and the Netherlands trap, poison and hunt it to protect their dykes.

Relationship with humans

Muskrat fur is warm, and it is at its best in early December in the north. Trapping became a large industry in the early 20th century. Pelts were trimmed and dyed and sold across the United States as Hudson seal. The winter hats of the Royal Canadian Mounted Police are muskrat. In South Korea, fur farms import muskrats, and a live animal sells for 600 to 1,000 US dollars.

The meat is edible, and Native Americans and others have eaten it for a long time. The musk glands in the tail must come out first, or they taint the lower belly. On farms, muskrats eat grain, block drain tiles and burrow into dykes until the banks fail. In Europe those burrows threaten the flood defences of low-lying countries. Muskrat lodges also keep marsh water open, which helps water birds.

In culture and myth

In many Native American creation stories, the muskrat is the earth-diver. After larger animals fail, it dives to the bottom of the first sea and returns with a little mud, which grows into the land. In Anishinaabe tradition, the muskrat, Wazhashk, gives its name to a clan. The Menominee also have a Muskrat Clan. Some Algonquin traditions make Muskrat a female figure, the mother of humankind.

Some Native people forecast the winter snow from the size and timing of muskrat lodges. In several tribes the muskrat is lucky, and tales tell of muskrats that reward people who treat them well. In Catholic tradition in south-east Michigan, a dispensation since the early 1800s lets the faithful eat muskrat on Lenten Fridays. In 2019, dinners along the Detroit River served up to 900 muskrats at a sitting, parboiled for four hours and then fried. Spirit-animal websites add perseverance and adaptability, but those meanings are probably modern, not folk tradition.